“A historic migration is under way around the world, from the countryside to swelling urban centers. Many of those new arrivals will find a better life. Others won’t.”

” “The urbanization that happened after the industrial revolution in the highly-industrialized countries was much, much more gradual than urbanization is now,” said Janice Perlman, an author and founder of the Mega-Cities Project. “Still, there was a lot of chaos and difficulty and a lot of environmental problems. But now it’s just accelerated exponentially.””

“”It’s as much to do with the lack of opportunity in rural areas as opposed to this great magnet of cities,” said Graeme Harrison, an economist who tracks the growth of megacities at Oxford Economics. “Because everything else—such as unemployment and high cost—would normally act against people migrating to cities.””

“A hundred years ago just 2 out of 10 people on Earth lived in cities. Today more than half the world’s population lives in cities, generating some 80 percent of global economic output. By the middle of this century, 7 out of 10 people will be urban dwellers, according to Hot Spots 2025, a report prepared by the Economist Intelligence Unit for Citibank.”

“A major challenge these cities will pose for society will be the strain on resources. Globally, cities today represent 2 percent of the Earth’s surface but use 75 percent of its resources, according to Euramet. As the urbanization trend accelerates, so, too, will issues of sustainability and infrastructure to support city dwellers.”

“The most competitive cities are also those blessed with well-developed infrastructure or the capital and political capacity to build it. That’s created a major challenge for some already congested cities in the developing world.”

“Officials in Jakarta, Indonesia, for example, have been planning to roll out a local mass-transit system for years, said Harrison.”

“”But to actually construct that metro would cause so much disruption in the short run, and the traffic congestion is so bad already, it’s almost beyond the point where you can install it,” he said. “When you have that type of problem, it’s very difficult to move forward. You’re always playing catch-up.””

“”I would be worried about the Arab spring repeating across many other parts of the World, just given the outlook for youth unemployment,” said Harrison. “A lot depends on how authorities respond to some of these challenges.”

“”Not every Chinese city can become a service hub,” he said. “So you could have some Detroits in China, given the number of industrial cities there.””

“Globalization also means megacities will increasingly compete with each other, fostering specialization in key industries or services—from finance to technology. Those changes in the economic global playing field will also shift the geopolitical balance.”